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Message-ID: <d3969a10-7cd2-3dfb-2e49-37ebad2d6440@gmail.com>
Date: Fri, 31 May 2024 17:10:08 +0200
From: Uros Bizjak <ubizjak@...il.com>
To: Borislav Petkov <bp@...en8.de>
Cc: Borislav Petkov <bp@...nel.org>, X86 ML <x86@...nel.org>,
LKML <linux-kernel@...r.kernel.org>, Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH 02/14] x86/alternatives: Add nested alternatives macros
Borislav Petkov je 31. 05. 24 ob 16:36 napisal:
> On Fri, May 31, 2024 at 04:30:31PM +0200, Uros Bizjak wrote:
>> Please don't resurrect the %P modifier, use %c instead.
>
> Btw, out of curiosity, is %P being phased out?
No ;)
> I'm looking at
>
> 41cd2e1ee96e ("x86/asm: Use %c/%n instead of %P operand modifier in asm templates")
>
> and yeah, %c is the generic one while %P is the x86-specific one but
> phasing latter out is probably going to take a bunch of gcc releases...
The intention of '%P' operand modifier is primarily to be used with PIC,
where:
'P' If used for a function, print the PLT
suffix and generate PIC code. For
example, emit 'foo@...' instead of 'foo'
for the function foo(). If used for a
constant, drop all syntax-specific
prefixes and issue the bare constant. See
'p' above.
the fact that is handles constants is due to historic reasons.
The '%c' operand modifier will also check its operand that it is indeed
an immediate integer operand, so should be used with 'i' operand constraint:
'c' Require a constant operand and print the
constant expression with no punctuation.
Uros.
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